There have been known two methods to regenerate a die for forming a glass product, in which a re-machining process or a re-polishing process is not necessary.
In the first method, employed is a die having an interlayer containing chromium as a main component between the substrate and the surface layer of the die. When the surface of the die is deteriorated due to repeated use, the die surface is treated with a processing solution which dissolves chromium. After dissolving and peeling the interlayer as well as the surface layer, a new interlayer and a new surface layer are formed on the substrate (refer to Patent Document 1). Japanese Patent Publication Open to Public Inspection, (hereinafter referred to as JP-A) No. 1-192733
In the second method, the surface film forming a die surface prepared on a substrate is removed by etching using ion beams, followed by forming a new surface film on the substrate to obtain a new die surface (refer to Patent Document 2). JP-A No. 5-32424
In the first method, the surface layer is commonly composed of materials which are insoluble in the processing solution. The surface layer is removed because the chromium interlayer is dissolved by the chromium dissolving processing solution which soaks in through surface cracks in the surface layer. However, it is very unlikely that in the ordinary forming process, such large cracks are formed in the surface layer. Consequently, the removal of the surface layer may not occur, or even if it is removed, the etching of the interlayer may take considerably long time.
On the other hand, in the second method, the surface film of the die is etched by ion beam to be peeled off. However, it is relatively difficult to suppress degradation of the surface roughness of the die due to the ion beam. Further, the ion beam etching has an inherent demerit in that it takes a very long time to peel away the layer due to the slow etching rate.
Patent Document 1: Japanese Patent Publication Open to Public Inspection (hereinafter referred to as JP-A) No. 1-192733
Patent Document 2: JP-A No. 5-32424